As is generally known, solar energy has reduced pollution and is readily available. But the conversion efficiency of solar batteries is too low, which may lead to the desirability of tracking the maximum power point. The output power of a solar battery is responsive to sunshine intensity and sunshine temperature, and for certain sunshine intensity and sunshine temperature, the maximum power outputted by the solar battery is definite. Thus, a method for improving the work efficiency of a solar battery may include controlling the solar battery to work in the maximum power point. In an instance in which the solar battery works on the maximum power point, the output voltage may be lower than the open circuit voltage, which may limit the range of the output voltage. At present, conventional solar electric-generation systems are unable to simultaneously track a maximum power point and expand an output voltage range of the maximum power point. Thus, the solar energy may be wasted.